Recently, in high-end servers, super computers, or the like, an optical interconnect that uses a high-speed optical transmission technique is being considered for short-range and medium-range signal transmissions between CPUs (Central Processing Units), in order to cope with the limits of electrical signal transmission caused by increasing signal transmission rate and increasing signal transmission capacity between the CPUs. According to the optical interconnect, an optical transceiver for converting electrical signals into optical signals, or the like, is provided to transmit data by optical signals between optical transmission apparatuses at a transmitter end and a receiver end, through transmission channels such as array optical fibers or the like, for example. A laser device called VCSEL (Vertical Cavity Surface Emitting Laser), that is small in size, has a low power consumption, and is cable of directly modulating current, for example, may be used for an optical transmitter for the optical transmission. A PD (Photo-Diode), that receives the optical signal and converts the received optical signal into the electrical signal, for example, may be used for an optical receiver for the optical transmission. A high-speed optical transmission having a signal transmission rate of 25 Gb/s, for example, is required in order to cope with broadband signal transmissions between the CPUs.
Examples of conventional receiver circuits for high-speed optical transmission may include optical receiver circuits having a limiting amplifier and a DC (Direct Current) feedback circuit, as proposed in Japanese Laid-Open Patent Publication No. 2011-109721 and Japanese Laid-Open Patent Publication No. 2012-010187, for example. The DC feedback circuit reduces an offset voltage between differential output signals differentially amplified by the limiting amplifier. The proposed optical receiver circuits may have properties such as a simple configuration, a high operation speed, and a high sensitivity.
However, the offset voltage between the differential output signals may also be affected by an amplification (or gain) of the DC feedback circuit and a magnitude of an input signal. For this reason, the offset voltage between the differential output signals is not sufficiently reduced in the conventional receiver circuits, and DCD (Duty Cycle Distortion) may be generated in the differential output signal. In a case in which a pulse width of the differential output signal deviates from a regular (or correct) value due to the generation of the DCD, there is a possibility that the differential output signal will not be correctly received at the receiver end of the differential output signal, for example.